1. Technical Field
This disclosure relates to magnetics in general, and in particular, to a method for arranging magnets in arrays to produce enhanced magnetic fields.
2. Related Art
“Halbach” magnet arrays have been widely used in permanent-magnet electrical machines since the mid 1980's to enhance performance and efficiency. The Halbach array has the property of producing a relatively high magnetic field on one side of the array while cancelling the field on the other side of the array to near zero.
As illustrated in FIG. 1, a Halbach array 10 is formed by successively rotating each of a linear row of magnets about an axis perpendicular to the long axis (the X axis) of the array such that the direction of their respective magnetic field vectors (as indicated by the arrows) is oriented 90 degrees relative to that of the immediately preceding magnet, from the first to the last magnet in the array. This produces an enhanced magnetic field on one side of the array 10 and substantially cancels the magnetic field on the opposite side (i.e., a “one-sided” magnetic flux).
In the above-referenced co-pending application, electrical motor/generators incorporating Halbach arrays and using both permanent and electro-magnets are disclosed that enable air gaps between the magnets and inductors of the devices to be increased without unduly increasing the weight of the devices. Other motor/generator applications incorporating Halbach arrays are described in the patent literature in, e.g., U.S. Pub. 2007/0029889 A1 by T. Dunn et al.; U.S. Pubs. 2003/0071532 A1 and 2003/0057791 A1 by R. Post; U.S. Pat. No. 7,352,096 to T. Dunn et al.; U.S. Pat. No. 7,291,953 to J. Smith et al.; and, U.S. Pat. No. 5,705,902 to B. Merritt et al.
Additionally, the ability of Halbach arrays to produce one-sided magnetic fluxes have resulted in their incorporation in a variety of so-called magnetic levitation or “maglev” track designs, as described in, e.g., U.S. Pat. Nos. 6,758,146; 6,664,880 and 6,633,217 to R. Post; and, U.S. Pat. No. 6,684,794 to O. Fiske et al.
Halbach arrays have also been advantageously incorporated in other electromotive devices to improve their performance, e.g., in passive magnetic bearings (U.S. Pat. No. 6,344,344 to R. Post), horizontal positioning devices (U.S. Pat. No. 6,531,793 to P. Frissen et al and U.S. Pat. No. 6,441,514 to D. Markle) and hydraulic pumps (U.S. Pat. No. 6,846,168 to W. Davis et al.)
Given their wide range of advantageous application to such a wide variety of electromotive devices, a need exists for improved Halbach arrays, including higher order Halbach arrays, that can yield even greater magnetic flux densities in such devices.